Planning for Systems Management & Operations as part of Climate Change Adaptation
3. Impact of Climate Change Effects on Transportation System Management and Operating Agencies
It is clear that many of the climate change effects listed in Section 2 require long-term changes to how transportation infrastructure is planned, designed, and constructed. Additionally, land-use planning and travel behavior modifications are important components of adaptation strategies. From a systems management and operations perspective, agencies face an uncertain future with respect to how they maintain, operate, and plan for the future. This section discusses the impact of climate change on transportation and systems management operations.
3.1. Increased System Maintenance Needs
Given the climate change effects listed in Section 2, specifically those related to increases in average air temperatures and shifts of the rain/snow line during the winter, transportation agencies will likely need to adapt by making changes to system maintenance. These changes could affect winter maintenance operations, require diversion to more resilient alternate routes, and prompt the deployment of “quick maintenance” patrols to address potentially more frequent potholes and buckling issues. Climate change effects to system maintenance needs are presented in Table 1.
| Climate Change Effects | Climate Change Impacts | System Maintenance Response |
|---|---|---|
| Climate Trends Impacts | ||
| Shifting rain/snow line | Fewer snow/ice precipitation events | Reduced need for winter maintenance operations resources and staff |
| Shifting rain/snow line | Less snowfall in areas that were previously impassable due to high and frequent snowfall | Potential for increased winter maintenance operations on routes currently inaccessible in winter |
| Shifting rain/snow line | Increased snowmelt/rain during the winter season increases the likelihood of flooding, which will generally affect specific roadways and locations, as opposed to the whole network | Shift in resources from winter maintenance to winter flooding monitoring and traveler information |
| Shifting rain/snow line | Temperatures in some areas may shift to or more frequently hover at the freezing point, increasing the probability of ice precipitation instead of snow | Shift in resources from snow to ice management |
| Shifting rain/snow line | Long-term shifting of snow/ice precipitation necessitates reassessment of winter maintenance needs | Monitoring trends to identify and forecast trends of increasing or decreasing snow/ice and frequency of extreme precipitation events |
| Shifting rain/snow line | Longer construction season due to higher temperatures, fewer days with temperatures below freezing, and less snow/ice precipitation | Altered construction and maintenance schedules |
| Changes in freeze/thaw cycle | Potential for longer duration and/or shifting of freeze/thaw period | Increased staff and resources to monitor vulnerable areas to post seasonal weight restrictions and make repairs. |
| Increased frequency, duration and intensity of droughts; increase in average air temperature | Roadside vegetation dies off | Changes to vegetation management activities |
| Increased frequency, duration and intensity of droughts; increase in average air temperature | Increased probability of wildfires | Increased staff and resources to monitor vulnerable areas and provide traveler information |
| Climate Event Impacts | ||
| Increased coastal and inland flooding; increases in intense precipitation events | Greater frequency of flooded, blocked (e.g., trees, landslides), damaged, and washed out roads | Mandatory diversion to more robust alternate routes, reducing route options/redundancy |
| Increased coastal and inland flooding; increases in intense precipitation events | Greater frequency of flooded, blocked (e.g., trees, landslides), damaged, and washed out roads | Increased staff and resources to monitor vulnerable routes and provide traveler information |
| Increase in magnitude and duration of severe heat waves | Greater risk of structural damage to bridge joints and pavement, e.g., buckling or rutting | Mandatory diversion, particularly for freight, to more robust alternate routes |
| Increase in magnitude and duration of severe heat waves | Greater risk of structural damage to bridge joints and pavement, e.g., buckling or rutting | Deploy “quick maintenance” patrols to address potholes and buckling issues |
| Increase in magnitude and duration of severe heat waves | Higher temperatures may inhibit construction activities during certain months, or times of day | Altered construction and maintenance schedules |
| Increase in dust storms | Greater frequency of reduced visibility conditions | Increased staff and resources to monitor vulnerable routes and provide traveler information |
Increases in average air temperature and reduced snowfall have the potential to impact greatly operations required for winter maintenance. Currently, 70% of the nation’s roads are in regions that receive over 5 in of annual average snowfall, requiring the expenditure of over $2.3 billion per year by state and local agencies for winter maintenance activities (FHWA, 2012). Additional millions of dollars are spent on infrastructure to repair damages caused by snow and ice (FHWA, 2012).
Multiple impacts highlighted in Section 2 could reduce the need for winter maintenance, most notably the increase in average air temperatures with the largest magnitude of warming in northern regions during winter and the general shifting of the rain/snow line north and to higher altitudes. For some areas, these impacts might indicate fewer days below freezing and thus reduced incidence of precipitation causing snow or ice conditions. For these areas, there may be a reduced need for resources to be dedicated to winter maintenance operations. However, there may also be opportunities to shift winter maintenance operations to areas that currently have seasonal closures, but will be easier to maintain with reduced snowfall under a changing climate.
Similarly, increases in average air temperature that cause the rain/snow line to shift north are likely to also influence subgrade freeze/thaw cycles. While a frozen subgrade provides a solid foundation for heavy vehicles on roadways, heavy vehicles traveling on a roadway with a poor subgrade can cause potholes and rutting that may require additional system maintenance for repairs. Alternatively, imposing weight restrictions during the spring freeze/thaw period may help ease this issue. Either way, additional staff and resources may be required to monitor the subgrade temperatures and pavements to know when weight restrictions should be imposed and repairs are required.
Furthermore, with the potential for increased frequency and intensity of extreme precipitation events, added winter maintenance operations resources may be imperative to maintain functionality of the transportation network. Winter storm disasters alone have caused over $29 billion in damages (adjusted for inflation) since 1980 (NOAA, 2012), and increases in intensity of extreme precipitation events may cause greater damages in the future. Winter flooding is projected in the Northwest due to more precipitation falling as rain and not snow, which would alter the response required from system maintenance personnel from winter maintenance operations to system monitoring and traveler information regarding flooding and closures.
Although severe damages from winter storms are often caused by ice damage to trees and power lines requiring cleanup and repairs, many winter storms produce only snowfall, which causes no significant damages, but simply impedes mobility on the transportation network until routes can be cleared. Increases in average air temperature may affect the type of precipitation that occurs in an area as the rain/snow line moves northward and to higher elevations, and the frequency of ice storms for particular regions may also shift northward.
Winter maintenance operations are already difficult to predict, since snowfall is quite variable – one year, 6 ft of snow might fall in a given location, and the next year no snow might fall at all. Climate change effects may influence trends overall such that snowfall extremes are more pronounced from year to year, or that the annual average amount of snow and ice precipitation is either reduced or increased for an area. Signs of changing trends must be monitored by transportation agencies, as they could severely impact winter operations of surface transportation. Necessarily, agencies may struggle to justify spending on resources and staff that remain unused or underutilized from year to year, and therefore be left unprepared for major snow events that occur on a less frequent basis.
A recurring consequence of many aforementioned climate change effects might be mandatory diversion to more robust alternate routes. This requirement might affect routes that traverse areas that are more prone to flooding due to sea level rise or increased precipitation, for example, or that contain lower quality pavements that are more susceptible to warmer temperatures. In both cases, transportation agencies will have to monitor vulnerable routes to provide traveler information via dynamic message signing, websites, or radio, for example, as well as have staff on hand to deploy signage and physically close impacted routes, as necessary. Impacts of warmer temperatures on pavements may require diversion of freight traffic more so than passenger traffic, in which case either static or dynamic weight restrictions might be imposed on those routes. Today, transportation agencies frequently recommend diversion for flooded areas using methods listed above; but with climate change effects, agencies should strategically expand their capacity for making these recommendations by deploying monitoring devices for roadways that are likely to be most affected.
Similarly, increases in magnitude and duration of severe heat waves are likely to increase issues related to potholes and buckling in pavements. The Iowa DOT reports that in a typical year an average of $400,000 is spent to make temporary and permanent repairs related to pavement buckling due to thermal expansion forces; costs may be $2000 for a single repair (IDOT, 2012). In particular, this might impact pavements that may not have been designed with a changing climate in mind. It is likely that warmer regions that experience these severe heat waves will begin incorporating pavement designs with increased tolerances for higher temperatures; however, some segments are likely to contain historic, lower quality pavement that is more susceptible to potholes and buckling. Transportation agencies may find it beneficial to deploy “quick maintenance” patrols for potholes and buckling issues, especially during extreme high temperature events when the buckling is most likely to occur. These “quick maintenance” patrols might operate in a manner similar to freeway service patrols (FSPs), or actually be an added service of FSPs. Just as FSPs are deployed on freeways to quickly address and clear incidents or stopped vehicles to maintain mobility, “quick maintenance” patrols would be available to quickly repair potholes or buckling pavement that is impacting mobility or safety on the roadway. For example, during extreme heat events, Virginia DOT puts crews on special alert to be prepared for emergency repairs to the state’s roadways (VDOT, 2012).
In general, increases in average air temperatures could alter the timing of construction activities throughout the year, particularly in northern areas where construction activities tend to be more limited in the winter (FHWA, 2011). Additionally, increases in the frequency and duration of heat waves could shift the timing of construction activities to occur at cooler parts of the day.
Finally, with changes to precipitation and temperature, roadside vegetation is likely to be affected. While drier conditions are likely to reduce the need for mowing operations, in general, increases in the frequency, duration, and intensity of drought conditions will precipitate the need for new, drought-resistant species that can survive dry conditions and serve as erosion control.
3.2. Changes to System Operations Practices and Strategies
Numerous impacts due to more widespread, higher intensity storms or tropical cyclones will create the need for broader disaster and evacuation preparedness. In general, planning for these events will come with increased uncertainty, as it pertains to personnel and resources. Likewise, rising sea levels and flood risks may increase the need to monitor vulnerable roadways in order to restrict access, given real-time conditions. Additionally, spikes in energy consumption due to warmer temperatures may cause localized power outages that could disrupt Traffic Management Centers’ communications. Climate change effects to system operations are presented in Table 2.
| Climate Change Effects | System Operations Response |
|---|---|
| Climate Event Impacts | |
| Increased recurring coastal and inland flooding; rising sea levels | Mandatory diversion to more robust alternate routes |
| Increased recurring coastal and inland flooding; rising sea levels | Increased staff and resources to monitor vulnerable routes and provide traveler information |
| Increase in intensity of tropical cyclones; increased occurrence of wildfires | Broader preparedness for potential evacuation |
| Increase in intensity of tropical cyclones; increased occurrence of wildfires | Increased TMC staff and Intelligent Transportation System (ITS) resources to provide traveler information during evacuations |
| Increase in intensity of tropical cyclones; increased occurrence of wildfires | More frequent disaster preparation, operations, and recovery actions |
| Climate Trends Impacts | |
| Increase in energy demand for air conditioning | Increased need for more resilient TMC communications and backup power to maintain real-time information feeds |
Increased inland and coastal flooding might increase the need to monitor a wider and different set of roadways and restrict access given forecasted or real-time conditions. With higher chances for flooding on a greater number of roadways, given more intense precipitation events, for example, there is a greater need for monitoring of these high-risk flood prone roadways for increased traveler information. Numerous examples of weather monitoring exist in which the TMC monitors flood gauges to alert travelers to real-time conditions.
Regarding hurricanes, increased intensity of storms coupled with rising sea levels will cause greater impacts over a broader area given the potential for shifting storm tracks, stimulating the need for a widened area for preparedness for evacuations. Thirty-one hurricane events have caused $417 billion (adjusted for inflation) in damage in the United States since 1980 (NOAA, 2012); more intense storms will likely increase the amount of damage and require faster and more comprehensive responses. This includes the need for greater TMC support for traveler information and for ITS to assist motorists during an evacuation. Additionally, more frequent disaster preparation, operations, and recovery actions will be needed to prepare those who may be impacted by these events. However, because of the likelihood of reduced frequency for such storms, there will be increased uncertainty in planning for hurricanes, in terms of personnel and resources. Similar actions may be required for inland areas that are impacted by flooding due to increased inland flooding, or for areas that are expected to experience increased wildfires.
Finally, with increases in extreme high temperature events and the intensity, frequency, and duration of heat waves, there will likely be an increase in energy demand for air conditioning during summer months. This could lead to spikes in energy usage that cause local power outages. This prompts the need for more resilient TMC communications and backup power in the field to maintain real-time information to drivers.
3.3. Changing Travel Behavior
Climate change effects are likely to affect greatly individuals’ transportation decisions and safety on the roadways. For example, because temperature and precipitation can impact decisions to use transit, bike, or walk, regional changes could increase or decrease individuals’ motivation to use alternate modes. This phenomenon has been investigated in a study on how weather affects Chicago transit ridership (Guo, et al., 2007). The data-driven study findings, which are shown in Table 3, showed that CTA bus ridership and weekend ridership are more sensitive to extreme weather than rail ridership and weekday, respectively, and that some weather conditions like fog or blizzards can increase transit ridership (Guo, et al., 2007). The study found that weekend ridership changed more than weekday ridership (Guo, et al., 2007). Localized climate change effects could also affect individuals’ routes and destinations, as well as exposure to weather-induced hazardous driving conditions. Climate change effects and potential responses that might change traveler behavior are presented in Table 4.
| Weather Condition | Bus Ridership Impact* Low |
Bus Ridership Impact* High |
Rail Ridership Impact* Low |
Rail Ridership Impact* High |
|---|---|---|---|---|
| Temperature (one degree increase) | +700 | +1100 | +200 | +700 |
| Rain (one inch increase) | -16,000 | -88,000 | -5000 | -45,000 |
| Snowfall (one inch increase) | -10,000 | -188,000 | Inconsistent/Not Significant | Inconsistent/Not Significant |
| Wind (one mph increase) | -700 | -2700 | Negligible | Negligible |
| Fog (moderate) | Not significant | Not significant | +8000 | +10,000 |
Source: Guo, et al., 2007.
| Climate Change Effect | Changes to Travel Behavior |
|---|---|
| Climate Event Impacts | |
| Increased exposure to hazardous driving conditions (e.g., flooding, road surface conditions, smoke from wildfires) | Less consistent mode split impacting day-to-day congestion and safety issues |
| Increased exposure to hazardous driving conditions (e.g., flooding, road surface conditions, smoke from wildfires) | Potential mode shift to/from alternate modes, e.g., using transit, biking, or walking |
| Increased exposure to hazardous driving conditions (e.g., flooding, road surface conditions, smoke from wildfires) | Increased TMC monitoring of more reliable routes to provide enhanced traveler information |
| Increased exposure to hazardous driving conditions (e.g., flooding, road surface conditions, smoke from wildfires) | Increased emphasis on carpooling and teleworking to reduce impacts to highways |
| Increased exposure to hazardous driving conditions (e.g., flooding, road surface conditions, smoke from wildfires) | Investigate regional climate change impacts to understand how impacts may affect traveler mode and route choice in both the short- and long-terms |
| Climate Trend Impacts | |
| Human health effects | Potential mode shift from alternate modes, e.g., transit, biking, or walking |
| Human health effects | Increased emphasis on carpooling and teleworking to reduce impacts to highways |
Many of the climate change effects listed in Section 2 will increase individuals’ exposure to hazardous driving conditions, which include reduced visibility, flooding, hazardous road surface conditions, landslides, and wildfires. All of these effects, individually, are likely to reduce driver safety and increase the likelihood for crashes. In addition, it is likely to reduce mobility with increased travel times due to the need to drive slower in adverse weather conditions or take alternate routes.
Clearly, climate change effects will vary by region with some mode shift to alternate, non-driving modes occurring in areas with less precipitation or more mild winters, for example; other areas may see mode shift to cars if extreme temperatures and increased precipitation occur. These mode shifts could affect operations on a day-to-day basis, potentially causing increased congestion and safety issues on highways for some days and on transit on other days. The relationship between weather and mode choice is complicated. Mode shift away from alternate, non-driving modes may also be induced by human health effects caused by higher pollen counts and pollution, i.e., higher concentrations of tropospheric (surface) ozone and non-volatile particulate matter (PM2.5). Moreover, travelers may avoid certain routes that are more vulnerable to climate change effects, e.g., flooding, which could increase congestion on more robust alternate routes. In general, transportation agencies should investigate the regional climate change effects to understand clearly how these effects may affect traveler mode and route choice, and thus affect operations on a day-to-day basis. Some regions may expect alternate, non-driving modes to see increased ridership, overall. In this case, an increased operations focus on traveler information and resources for these modes may be in order. Other regions may expect a reduction in the use of alternate, non-driving modes. For this case, increased emphasis on carpooling and teleworking may be necessary to reduce impacts to highways.
Over time, climate change effects could cause long-term changes in travel behavior. Individuals or businesses may choose not to reside in low-lying coastal areas that are more vulnerable to sea level rise and increased storm surge associated with coastal storms and hurricanes. Given individuals’ inclination to live near the coast despite the risk of hurricanes, it is uncertain whether this inland shift will occur, or whether individuals will choose to adapt in place. Regardless, transportation agencies should be mindful of the potential for long-term travel shifts, in addition to those that occur in the short-term.
3.4. Changes to Freight Transportation
In addition to the impacts that climate change effects are expected to have on the transportation network as a whole, there might be unique impacts to freight transportation. Multiple climate change effects could disrupt inland waterways, impacting freight flows and diverting freight to trucks on highways. Roadways with pavements affected by increased temperatures might require dynamic or seasonal truck weight or speed restrictions for specific roadways or different regulations for the industry as a whole. Expected climate change effects to freight transportation are presented in Table 5.
First, there are several potential climate change effects that might affect shipments on inland waterways. Increased occurrence of flooding and drought, coupled with changes in seasonal precipitation and river flow patterns, could disrupt freight flows to other inland waterways, such as the Mississippi and Ohio Rivers, which might add trucks to highways. Lower water levels in the Great Lakes might restrict boat access to ports and shipping channels in that system. The 2007 Commodity Flow Survey showed that about 423 million tons of goods (3% of all tonnage) and about 176 billion ton-miles (5% of all ton-miles) were carried by water, with the Mississippi River system being the most active freight waterway (RITA, 2007). Either high water or low water could affect shipping, but reduced reliability of this mode might also encourage a shift to trucks or rail.
| Climate Change Effect | Freight Transportation Response |
|---|---|
| Climate Event Impacts | |
| Increased frequency, duration, and intensity of droughts; increased coastal and inland flooding | Restricted access to ports and shipping channels for inland waterways |
| Increased frequency, duration, and intensity of droughts; increased coastal and inland flooding | Mode shift from inland waterways to trucking due to reduced reliability |
| Longer duration and/or shifting of springtime freeze/thaw period | Mandatory freight diversion to more robust alternate routes |
| Increase in magnitude and duration of severe heat waves | Mandatory freight diversion to more robust alternate routes or modes |
| Increase in magnitude and duration of severe heat waves | Dynamic or seasonal restrictions for trucks or rail during times of high heat, reducing either acceptable speed or weight |
| Increase in magnitude and duration of severe heat waves | Policy and regulation changes to restrict truck size and weights for the entire roadway network or specific highway classes |
| Increase in magnitude and duration of severe heat wave | Deploy “quick maintenance” patrols to address potholes and buckling issues |
Increases in average air temperature during the winter are likely to influence subgrade freeze/thaw cycles. As mentioned previously, a frozen subgrade provides a solid foundation for heavy vehicles on roadways, weight restrictions may be required for roadways with a poor subgrade to prevent potholes and rutting. Areas that experience more days above freezing during the winter may have to extend or shift the period of time during which weight restrictions are imposed.
As mentioned previously, the impact of severe heat waves on pavements that were not designed to withstand such heat might cause potholes or buckling issues. Although this issue might be addressed in the long-term as new pavement designs are implemented to withstand these higher temperatures, in the short-term there may be some roadways in which this remains an issue. For these roadways, there may be a need to implement dynamic or seasonal restrictions for trucks during times of high heat, reducing either acceptable truck speed or weight. Currently, truck weight or size restrictions are not uncommon for routes with deficient infrastructure, e.g., bridges and tunnels, and similar restrictions might need to be imposed for affected roadways using dynamic or static signage. Alternatively, changes to policy and regulations could be implemented to restrict truck size and weights for an entire roadway network or for specific highway classes. Such restrictions may also affect freight transport through trains.
